Metallic surface of a bipolaronic insulator

TL;DR

This paper explores how the surface of a strongly coupled electron-phonon system can exhibit different electronic properties from the bulk, showing that a metallic surface can exist on a bipolaronic insulator while an insulating surface cannot on a metallic bulk.

Contribution

It demonstrates the conditions under which a metallic surface can be stabilized on a bipolaronic insulator, highlighting the asymmetry in surface-bulk property stabilization.

Findings

A metallic surface can be decoupled from a bipolaronic insulator.

A truly insulating surface on a metallic bulk appears impossible.

Surface properties can differ significantly from bulk due to parameter inhomogeneity.

Abstract

We investigate the possibility that the surface of a strongly coupled electron-phonon system behaves differently from the bulk when the relevant parameters are inhomogeneous due to the presence of the interface. We consider parameter variations which make the surface either more metallic or more insulating than the bulk. While it appears impossible to stabilize a truly insulating surface when the bulk is metallic, the opposite situation can be realized. A metallic surface can indeed be decoupled from a bipolaronic insulator realized in the bulk.